1. Field of the Invention
The present invention relates to wireless LANs, and more specifically, to a method and apparatus for accessing a medium in a wireless LAN.
2. Related Art
Recent wireless LAN techniques are evolving typically in three ways. Efforts to achieve accelerated transmission in consistence with those phases have spawned IEEE (Institute of Electrical and Electronic Engineers) 802.11ac and IEEE 802.11ad. IEEE 802.11ad is a wireless LAN technique adopting a 60 GHz band. As a technique for providing wider coverage than that of existing wireless LAN, wideband wireless LAN employing a frequency band less than 1 GHz are recently gaining popularity. Wideband wireless LAN comes in two standards: IEEE 802.11af adopting a TVWS (TV white space) band and IEEE 802.11lh adopting a 900 MHz band. These wireless LAN techniques primarily target smart grids, wider-area sensors, and extended range Wi-Fi services. Existing wireless LAN MAC (Medium Access Control) techniques are sometimes challenged by a significantly increased initial link setup time. Vigorous efforts for IEEE 802.11ai standardization are recently ongoing to address this issue and resultantly enable quick access of an STA to an AP.
IEEE 802.11ai is the MAC technology dealing with rapid authentication procedures in order to substantially save initial setup and association times, and a regular task group for standardization was launched in January 2011. In order to enable quick access, IEEE 802.11ai deals with simplifying processes in light of AP discovery, network discovery, TSF (Time Synchronization Function) synchronization, authentication & association, procedure merging with higher layers, and so on. Among others, ideas such as procedure merging utilizing piggyback of DHCP (Dynamic Host Configuration Protocol), optimization of full EAP (Extensible Authentication Protocol) using concurrent IP, and efficient selective AP (Access Point) scanning, are under intense discussion.